Error Code 403 / user account [..]

After access we got: 
Code: 403, Message: Forbidden, Body: {"error":{"code":"ErrorSendAsDenied","message":"The user account which was used to submit this request does not have the right to send mail on behalf of the specified sending account., Cannot submit message."}}

Pls help!
============================


Mailer: postsmtp

HostName: 

cURL Version: 7.88.1

OpenSSL Version: OpenSSL/3.0.16

OS: Linux 6.1.0-37-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.140-1 (2025-05-22) x86_64

PHP: Linux 8.2.28 C.UTF-8

PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=No, mcrypt=Yes, zlib_encode=Yes

WordPress: 6.7.2 en_US UTF-8

WordPress Theme: Bento

WordPress Plugins: Gravity Forms, Ivory Search, Borlabs Cookie - Cookie Opt-in, Classic Editor, Code Snippets, Gravity Forms + Custom Post Types, Gravity Forms Polls Add-On, Health Check & Troubleshooting, OMGF, WPCode Lite, Matomo Analytics - Ethical Stats. Powerful Insights., Members, Post SMTP Pro, Post SMTP, Quick Page/Post Redirect Plugin, Regenerate Thumbnails, Security Ninja (Premium), Simple Local Avatars, Page Builder by SiteOrigin, SiteOrigin Widgets Bundle, Category Order and Taxonomy Terms Order, Team Showcase, USP Pro, Wordfence Security, Yoast SEO, WP Comment Notifier For All, WP Crontrol, WP Fastest Cache, Force Login, WP Post Notifier For All, WP STAGING PRO - Backup Duplicator & Migration, WP STAGING WordPress Backup Plugin - Backup Duplicator & Migration, NextGEN Gallery

WordPress wp_mail Owner: /usr/www/users/fusecom/wpcms/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php

WordPress wp_mail Filter(s): wp_staticize_emoji_for_email, PostsmtpMailer->get_mail_args

WordPress wp_mail_from Filter(s): wordfence::fixWPMailFromAddress

Postman: 3.2.0

Postman Sender Domain (Envelope|Message): ******

Postman Prevent Message Sender Override (Email|Name): No | No

Postman Active Transport: Office365 API (https://smtp.office365.com:443)

Postman Active Transport Status (Ready|Connected): Yes | Yes

Postman Deliveries (Success|Fail): 0 | 2